undefect. CWE-407 — 63 sites patched across 27 ecosystems

Authors: russell@unturf.com · brackishbert@gmail.com · foxhop.net · TimeHexOn.com

Patches, unit tests, benchmarks, whitepaper, and outreach briefs.
Public domain — no copyright claimed. Use freely.

test/jdk/java/lang/Thread/virtual/CancelTimerWithContention.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2024, 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @summary Test cancelling a timeout task for Object.wait(millis) when there is
+ *     contention on the timer queue
+ * @requires vm.continuations
+ * @key randomness
+ * @run main/othervm/timeout=480
+ *     -Djdk.virtualThreadScheduler.parallelism=2
+ *     -Djdk.virtualThreadScheduler.timerQueues=1
+ *     CancelTimerWithContention
+ */
+
+import java.time.Instant;
+import java.util.Random;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class CancelTimerWithContention {
+
+    // number of threads
+    private static final int MIN_THREADS = 100;
+    private static final int MAX_THREADS = 10_000;
+
+    // number of monitors to enter
+    private static final int MIN_MONITORS = 2;
+    private static final int MAX_MONITORS = 8;
+
+    private static final Random RAND = new Random();
+
+    public static void main(String[] args) {
+        for (int threadCount = MIN_THREADS; threadCount <= MAX_THREADS; threadCount += 100) {
+            System.out.format("%s #threads = %d%n", Instant.now(), threadCount);
+            for (int lockCount = MIN_MONITORS; lockCount <= MAX_MONITORS;  lockCount += 2) {
+                test(threadCount, lockCount);
+            }
+        }
+    }
+
+    /**
+     * Test threads entering monitors and using Object.wait(millis) to wait. This
+     * testing scenario leads to a mix of contention (with responsible threads using
+     * short timeouts), timed-wait, and cancellation of timer tasks. This scenario
+     * can result in contention of the timer queue.
+     */
+    static void test(int threadCount, int monitorCount) {
+        var locks = new Object[monitorCount];
+        for (int i = 0; i < monitorCount; i++) {
+            locks[i] = new Object();
+        }
+
+        try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
+            var finished = new AtomicInteger();
+
+            for (int i = 0; i < threadCount; i++) {
+                Object lock = locks[RAND.nextInt(monitorCount)];    // random lock
+
+                executor.submit(() -> {
+                    synchronized (lock) {
+                        lock.wait(Long.MAX_VALUE);
+                    }
+                    finished.incrementAndGet();
+                    return null;
+                });
+
+                synchronized (lock) {
+                    lock.notify();
+                }
+            }
+
+            // notify at most one thread until all threads are finished
+            while (finished.get() < threadCount) {
+                for (Object lock : locks) {
+                    synchronized (lock) {
+                        lock.notify();
+                    }
+                }
+            }
+        }
+    }
+}